This month skin irritations tickled uncontrollably (2,8)
I believe the answer is:
in stitches
'irritations tickled uncontrollably' is the definition.
I don't know anything about this answer so I cannot tell whether it can be defined by this definition.
'this month skin' is the wordplay.
'this month' becomes 'inst' (letter-writing abbreviation for this month).
'skin' becomes 'itches' (I can't explain this - if you can you should believe this answer much more).
'inst'+'itches'='IN STITCHES'
Can you help me to learn more?
(Other definitions for in stitches that I've seen before include "Laughing a lot" , "you may be laughing" , "Following a visit to the theatre one may be" , "Helpless with laughter" , "as one may be on leaving the theatre?" .)